Textured self-cleaning film system and method of forming same

ABSTRACT

A self-cleaning film system includes a substrate and an anti-reflection film disposed on the substrate. The anti-reflection film includes a first sheet formed from titanium dioxide, a second sheet formed from silicon dioxide and disposed on the first sheet, and a third sheet formed from titanium dioxide and disposed on the second sheet. The system includes a self-cleaning film disposed on the anti-reflection film and including a monolayer disposed on the third sheet and formed from a fluorinated material selected from the group consisting of fluorinated organic compounds, fluorinated inorganic compounds, and combinations thereof. The self-cleaning film includes a first plurality of regions disposed within the monolayer such that each of the first plurality of regions abuts and is surrounded by the fluorinated material and includes a photocatalytic material.

INTRODUCTION

The disclosure relates to a self-cleaning film system and to a method offorming the self-cleaning film system.

Devices, such as display systems, are often designed to be touched by anoperator. For example, a vehicle may include a display system thatpresents information to an operator via a touchscreen. Similarly, anautomated teller machine or kiosk may include a display system that isactivated by touch.

Other devices, such as cameras and eyeglasses, generally include a lenssurface which may be inadvertently touched by an operator during use.Further, other devices such as vehicles, windows, mirrors, appliances,cabinetry, furniture, cellular telephones, fingerprint scanners,sensors, copiers, medical instruments, and countertops may also includeone or more surfaces which may be touched by an operator. Therefore,during use, an operator may deposit fingerprints and/or oils onto suchdevices and surfaces.

SUMMARY

A self-cleaning film system includes a substrate and an anti-reflectionfilm disposed on the substrate. The anti-reflection film includes afirst sheet formed from titanium dioxide, a second sheet formed fromsilicon dioxide and disposed on the first sheet, and a third sheetformed from titanium dioxide and disposed on the second sheet. Theself-cleaning film system also includes a self-cleaning film disposed onthe anti-reflection film and including a monolayer disposed on the thirdsheet and formed from a fluorinated material selected from the groupconsisting of fluorinated organic compounds, fluorinated inorganiccompounds, and combinations thereof. The self-cleaning film alsoincludes a first plurality of regions disposed within the monolayer suchthat each of the first plurality of regions abuts and is surrounded bythe fluorinated material, wherein each of the first plurality of regionsincludes a photocatalytic material.

In one aspect, the self-cleaning film may have a first surface and asecond surface spaced opposite the first surface and abutting theanti-reflection film. The first surface may be substantially free fromsqualene and water.

The substrate may have a proximal surface abutting the anti-reflectionfilm, a distal surface spaced opposite the proximal surface, a firstedge connecting the proximal surface and the distal surface, and asecond edge spaced opposite the first edge.

In another aspect, the self-cleaning film system may further include alight source disposed adjacent the first edge and configured foremitting electromagnetic radiation. The electromagnetic radiation mayhave a wavelength of from 400 nm to 100 nm. Alternatively, theelectromagnetic radiation may have a wavelength of from 740 nm to 380nm.

The self-cleaning film may define a contact angle with water of greaterthan 140°. The photocatalytic material may be titanium dioxide and maybe present in a rutile form. In another aspect, the photocatalyticmaterial may be titanium dioxide and may be present in an anatase form.Alternatively, the photocatalytic material may be titanium dioxide andmay be present as a combination of the rutile form and the anatase form.

In an additional aspect, the photocatalytic material may be doped withsilver. Alternatively, the self-cleaning film system may further includea second plurality of regions disposed within the monolayer such thateach of the second plurality of regions abuts and is surrounded by thefluorinated material. Each of the second plurality of regions mayinclude silver. In one aspect, the fluorinated material is fluorinateddiamond-like carbon.

In yet another aspect, the monolayer may have a texture defined by acombination of a plurality of microstructures and a plurality ofnanostructures.

In a further aspect, the anti-reflection film may further include afourth layer disposed on the third layer and formed from silicondioxide. The first sheet may have a first thickness, the second sheetmay have a second thickness that is greater than the first thickness,and the third sheet may have a third thickness that is greater than thefirst thickness and the second thickness.

In another embodiment, a self-cleaning film system includes a substrateand an anti-reflection film disposed on the substrate. Theanti-reflection film includes a first sheet formed from titaniumdioxide, a second sheet formed from silicon dioxide and disposed on thefirst sheet, and a third sheet formed from titanium dioxide and disposedon the second sheet. The first sheet has a first thickness, the secondsheet has a second thickness that is greater than the first thickness,and the third sheet has a third thickness that is greater than the firstthickness and the second thickness. The self-cleaning film system alsoincludes a self-cleaning film disposed on the anti-reflection film andincluding a monolayer disposed on the third sheet and formed from afluorinated material selected from the group consisting of fluorinatedorganic compounds, fluorinated inorganic compounds, and combinationsthereof. The monolayer has a texture defined by a plurality ofmicrostructures spaced apart from one another along the monolayer and aplurality of nanostructures disposed on each of the plurality ofmicrostructures. The self-cleaning film also includes a first pluralityof regions disposed within the monolayer such that each of the firstplurality of regions abuts and is surrounded by the fluorinatedmaterial, wherein each of the first plurality of regions includes aphotocatalytic material.

In one aspect, each of the plurality of microstructures has a conicalshape and a first height of from 0.5 μm to 2 μm and further wherein eachof the plurality of nanostructures has a second height of from 1 nm to 4nm. In another aspect, the anti-reflection film may have a fourth layerdisposed on the third layer and formed from silicon dioxide.

A method of forming a self-cleaning film includes depositing ananti-reflection film on a substrate. The anti-reflection film includes afirst sheet formed from titanium dioxide, a second sheet formed fromsilicon dioxide and disposed on the first sheet, a third sheet formedfrom titanium dioxide and disposed on the second sheet. The methodfurther includes magnetron sputtering a self-cleaning film on theanti-reflection film. The self-cleaning film includes a monolayerdisposed on the third sheet and formed from a fluorinated materialselected from the group consisting of fluorinated organic compounds,fluorinated inorganic compounds, and combinations thereof. Theself-cleaning film also includes a first plurality of regions disposedwithin the monolayer such that each of the first plurality of regionsabuts and is surrounded by the fluorinated material. Each of the firstplurality of regions includes a photocatalytic material. The method alsoincludes, after magnetron sputtering, reactive ion etching theself-cleaning film with SF₆—O₂ gas to produce a texture defined by aplurality of microstructures spaced apart from one another along themonolayer and a plurality of nanostructures disposed on each of theplurality of microstructures.

In one aspect, reactive ion etching includes forming each of theplurality of microstructures to have a conical shape and a first heightof from 0.5 μm to 2 μm and forming each of the plurality ofnanostructures to have a second height of from 1 nm to 4 nm.

The above features and advantages and other features and advantages ofthe present disclosure are readily apparent from the following detaileddescription of the best modes for carrying out the disclosure when takenin connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a perspective view of aself-cleaning film system.

FIG. 2 is a schematic illustration of a cross-sectional view of theself-cleaning film system of FIG. 1 taken along section line 2-2.

FIG. 3 is a schematic illustration of a perspective view of anotherembodiment of the self-cleaning film system of FIG. 1.

FIG. 4 is a schematic illustration of a magnified view of a surface ofthe self-cleaning film systems of FIGS. 1 and 3.

FIG. 5 is a schematic illustration of a method of forming theself-cleaning film system of FIGS. 1 and 3.

DETAILED DESCRIPTION

Referring to the Figures, wherein like reference numerals refer to likeelements, a self-cleaning film system 10, 110 is shown generally inFIGS. 1 and 3. The self-cleaning film system 10, 110 may be suitable forapplications in which an operator may touch and deposit fingerprints,oils, and/or other organic or carbon-based contaminants or pathogens 100(FIG. 4) onto a screen, lens, or surface. More specifically, theself-cleaning film system 10, 110 may be useful for applicationsrequiring a clean, substantially oil-free, fingerprint-free, andwater-free screen, lens, or surface. That is, the self-cleaning filmsystem 10, 110 may be useful for removing fingerprints and other organiccontaminants 100 from such screens, lenses, or surfaces, and may becharacterized as superoleophobic and superhydrophobic.

For example, the self-cleaning film system 10, 110 may be useful forautomotive applications such as in-dash navigation systems which includea touchscreen, vehicle cameras which include a lens, vehicle mirrors,and vehicle interior surfaces. Alternatively, the self-cleaning filmsystem 10, 110 may be useful for non-automotive applications such as,but not limited to, consumer electronics, cellular telephones, eyewear,personal protective equipment, appliances, furniture, kiosks,fingerprint scanners, medical devices, sensors, aircraft, and industrialvehicles.

Referring now to FIG. 1, the self-cleaning film system 10 includes asubstrate 12. The substrate 12 may be formed from a vitreous,transparent material suitable for refracting visible light. For example,in one embodiment, the substrate 12 may be formed from silicon dioxide.In another example, the substrate 12 may be formed from a polycarbonateor other plastic. In one embodiment, the substrate 12 may be formed fromcellulose triacetate. The substrate 12 may have a suitable substratethickness 14 (FIG. 2) according to a desired application of theself-cleaning film system 10. For example, the substrate 12 may have asubstrate thickness 14 of from 100 nm to 500 nm. In general, thesubstrate 12 may be configured as, by way of non-limiting examples, ascreen of a display system, a lens of eyeglasses or goggles, a visor ofa helmet, a surface of a refrigerator, a face of a cabinet, a door panelof a vehicle, a touchscreen of a kiosk, or as another surface or devicethat may be touched by an operator.

The self-cleaning film system 10 also includes an anti-reflection film16 disposed on the substrate 12. The anti-reflection film 16 may beconfigured for reducing a reflection off the self-cleaning film system10 and thereby improving an efficiency of the self-cleaning film system10 since lost light in the system 10 may be minimized. As such, theself-cleaning film system 10 has both self-cleaning capabilities andcomparatively low reflectance. The anti-reflection film 16 may be formedfrom an anti-reflection coating comprising alternating layers 18, 20, 22of silicon dioxide and titanium dioxide. Each of the alternating sheets18, 20, 22 of silicon dioxide and titanium dioxide may have a thickness26, 28, 30 (FIG. 2) of from 5 nm to 125 nm. Further, the thickness 26,28, 30 of each layer 18, 20, 22 may be optimized as set forth below toachieve broadband, spectral performance over wide incident angles.

For example, as described with reference to FIG. 2, the anti-reflectionfilm 16 includes a first sheet 18 formed from titanium dioxide. Thefirst sheet 18 may have a first thickness 26 of from 5 nm to 25 nm,e.g., 10 nm, and may have a comparatively low index of refraction. Theanti-reflection film 16 includes a second sheet 20 formed from silicondioxide and disposed on the first sheet 18. The second sheet 20 may havea second thickness 28 that is greater than the first thickness 26 and acomparatively high index of refraction. For example, the secondthickness 28 may be from 20 nm to 45 nm, e.g., 33 nm. Theanti-reflection film 16 includes a third sheet 22 formed from titaniumdioxide and disposed on the second sheet 20. The third sheet 22 may havea third thickness 30 that is greater than the first thickness 26 and thesecond thickness 28 and a comparatively low index of refraction. Thethird thickness 30 may be from 50 nm to 200 nm, e.g., 100 nm. Althoughnot shown, the anti-reflection film 16 may also include more than threelayers or sheets 18, 20, 22. For example, in one embodiment describedwith reference to FIG. 3, the anti-reflection film 16 may include afourth sheet 24 disposed on the third sheet 22. The fourth sheet 24 maybe formed from silicon dioxide and may have a fourth thickness 32 offrom 50 nm to 150 nm, e.g., 75 nm. The fourth sheet 24 may have acomparatively high index of refraction. In one embodiment, the fourththickness 32 is less than the third thickness 30 and greater than thesecond thickness 28.

Referring again to FIG. 1, the self-cleaning film system 10 alsoincludes a self-cleaning film 34 disposed on the anti-reflection film16, e.g., chemically bonded to the anti-reflection film 16 as set forthin more detail below. The self-cleaning film 34 may be configured tocover and protect the substrate 12 and anti-reflection film 16 fromfingerprints, oils, and organic contaminants 100 (FIG. 4). That is, theself-cleaning film 34 may be configured to cause fingerprints, oils,water, and organic contaminants 100 deposited on the self-cleaning film34 to vanish, disappear, or vaporize so as to maintain a clean substrate12 that is capable of displaying crisp images or reflections. Inparticular, in some embodiments, the self-cleaning film 34 may replace atopmost layer of the anti-reflection film 16 so as to integrateanti-reflection and self-cleaning capabilities into a single layer. Assuch, the self-cleaning film system 10 may minimize complexity and layerstack manufacturing and design. For example, tack time and materialconsumption costs may be comparatively lower for the self-cleaning filmsystem 10.

More specifically, as described with reference to FIG. 2, theself-cleaning film 34 may have a first surface 36 and a second surface38 spaced opposite the first surface 36. The second surface 38 may abutthe anti-reflection film 16, and the first surface 36 may besubstantially free from squalene and water, organic material, and/orother oils of fatty acids. As used herein, the terminology squalenerefers to an organic compound having 30 carbon atoms and represented bythe International Union of Pure and Applied Chemistry name(6E,10E,14E,18E)-2,6,10,15,19,23-hexamethyltetracosa-2,6,10,14,18,22-hexaene.In general, the self-cleaning film 34 may be characterized as a thinfilm and may have a film thickness 40 of, for example, from 5 nm to 30nm, such as 10 nm.

The substrate 12 may also have a proximal surface 42 abutting theanti-reflection film 16 and a distal surface 44 spaced opposite theproximal surface 42. Therefore, the substrate 12, the anti-reflectionfilm 16, and the self-cleaning film 34 are configured to transmitvisible light through the proximal surface 42, the distal surface 44,the first surface 36, and the second surface 38. The substrate 12 mayalso have a first edge 46 connecting the proximal surface 42 and thedistal surface 44, and a second edge 48 spaced opposite the first edge46.

The self-cleaning film 34 may define a contact angle 50 with water ofgreater than or equal to 115°, e.g., greater than 140°. For example, theself-cleaning film 34 may define a contact angle 50 with water ofgreater than or equal to 150°. As such, water, oils, and contaminants100 (FIG. 4) may effectively bead on and translate across the firstsurface 36. Stated differently, water, oils, and contaminants 100 may bemobile and effectively translate along the first surface 36 such thatthe self-cleaning film 34 is superoleophobic and superhydrophobic.

Referring to FIG. 2, the self-cleaning film system 10 may furtherinclude a light source 52 disposed adjacent the first edge 46 andconfigured for emitting electromagnetic radiation. For example, thelight source 52 may be an ultraviolet light-emitting diode and theelectromagnetic radiation may have a wavelength of from 400 nm to 100nm. Alternatively, the light source 52 may be an incandescent bulb or avisible light-emitting diode and the electromagnetic radiation may havea wavelength of from 740 nm to 380 nm.

The self-cleaning film 34 is formed from a self-cleaning coatingcomposition. That is, the self-cleaning film 34 may mitigatefingerprint, water, and oil deposition, i.e., self-clean. Theself-cleaning coating composition and self-cleaning film 34 include aphotocatalytic material 54 (FIG. 1) and a fluorinated material 56 (FIG.1), as set forth in more detail below.

Referring now to FIG. 1, the self-cleaning film 34 includes a monolayer58 disposed on the third sheet 22 and formed from a fluorinated material56 selected from the group consisting of fluorinated organic compounds,fluorinated inorganic compounds, and combinations thereof. As best shownin FIG. 1, the monolayer 58 may form a majority of the self-cleaningfilm 34 and may be characterized as a monolayer field. As used herein,the terminology monolayer refers to a layer having a thickness 40 (FIG.2) of one molecule. That is, the monolayer 58 is one molecule thick andmay be characterized as a thin layer. In one embodiment, the fluorinatedmaterial is fluorinated diamond-like carbon. In another embodiment, thefluorinated material is fluorinated tin (IV) oxide. The fluorinatedmaterial, i.e., fluorinated organic compounds, fluorinated inorganiccompounds, and combinations thereof such as fluorinated diamond-likecarbon or fluorinated tin (IV) oxide, provides the self-cleaning film 34with superhydrophobicity, water-resistance, anti-microbial properties,anti-soiling properties, and scratch-resistance. The self-cleaning film34 may also contribute to a clean air quality of an ambient environmentin which the self-cleaning film 34 is used.

As shown in FIG. 1, the self-cleaning film 34 also includes a firstplurality of regions 62 disposed within the monolayer 58 such that eachof the first plurality of regions 62 abuts and is surrounded by thefluorinated material. That is, the first plurality of regions 62 may besituated within and along the monolayer 58. In one embodiment, the firstplurality of regions 62 may be equally spaced apart from each otheralong the first surface 36. In other embodiments, the first plurality ofregions 62 may be randomly spaced throughout the monolayer 58 along thefirst surface 36. In still other embodiments, the first plurality ofregions 62 may be arranged in a pattern within the monolayer 58. Thefirst plurality of regions 62 may be present in the self-cleaning film34 in an amount of from about 10 parts by volume to about 85 parts byvolume based on 100 parts by volume of the self-cleaning film 34, e.g.,about 50 parts by volume based on 100 parts by volume of theself-cleaning film 34.

Each of the first plurality of regions 62 includes a photocatalyticmaterial, such as titanium dioxide. The photocatalytic material 54 mayprovide the self-cleaning film 34 with self-cleaning capability. Thatis, the photocatalytic material 54 may oxidize and/or vaporize organicmaterial, e.g., squalene, present on the first surface 36 of theself-cleaning film 34, as set forth in more detail below. In particular,the photocatalytic material 54 may be a light-activated photocatalystupon exposure to, for example, visible or ultraviolet light.

Suitable photocatalytic materials 54 may include, but are not limitedto, photo-oxidative semiconductors, semiconducting oxides, doped metaloxides, heterojunction materials, and combinations thereof.

In one embodiment, the photocatalytic material 54 may be titaniumdioxide and may be present in the first plurality of regions 62 in arutile form. Alternatively, the photocatalytic material 54 may betitanium dioxide and may be present in the first plurality of regions 62in an anatase form, which may exhibit a comparatively higherphotocatalytic activity than the rutile form. In other embodiments, thephotocatalytic material 54 may be titanium dioxide and may be present inthe first plurality of regions 62 as a combination of the rutile formand the anatase form. Further, the photocatalytic material 54 may bedoped to form a functionalized photocatalytic material, e.g.,functionalized titanium dioxide. For example, the functionalizedphotocatalytic material may be doped with a metal such as, but notlimited to, chromium, cobalt, copper, vanadium, iron, silver, platinum,molybdenum, lanthanum, niobium, and combinations thereof. In oneembodiment, the photocatalytic material 54 may be doped with silver.Alternatively, the functionalized photocatalytic material may be dopedwith a non-metal such as, but not limited to, nitrogen, sulfur, carbon,boron, potassium, iodine, fluorine, and combinations thereof.

The photocatalytic material 54 may be characterized as a nanoparticleand may have an average diameter measureable on a nanometer scale.Alternatively, the photocatalytic material 54 may be characterized as aparticle and may have an average diameter measureable on a micrometerscale. Generally, the photocatalytic material 54 may be present in theself-cleaning film 34 in an amount of from about 2 parts by volume toabout 35 parts by volume based on 100 parts by volume of theself-cleaning film 34.

In other non-limiting embodiments, the photocatalytic material 54 mayinclude a semiconducting oxide such as, but not limited to, zinc oxide,bismuth, tin oxide, and combinations thereof. The semiconducting oxidemay be selected to have a band gap separation suitable for aphotocatalytic reaction, as set forth in more detail below.

As set forth above, in some embodiments, the self-cleaning film 34 mayreplace the topmost layer, e.g., the fourth sheet 24 (FIG. 3), of theanti-reflection film 16. Further, the fluorinated material 56 may havean index of refraction of from about 1.2 to about 1.6, e.g., from about1.3 to about 1.5, according to the percentage of fluorine present in thefluorinated material. Consequently, the self-cleaning film system 10 mayinclude a comparatively thicker monolayer 58 formed from the fluorinatedmaterial 56, which may in turn contribute to comparatively greaterphotocatalytic activity of the photocatalytic material 54. Thefluorinated material 56 may also be transparent and have excellentdurability. As such, for some embodiments, the fluorinated material mayallow for replacement of the topmost layer, e.g., the fourth sheet 24,of the anti-reflection film 16.

In another embodiment, the self-cleaning film 34 may include a secondplurality of regions 64 disposed within the monolayer 58 such that eachof the second plurality of regions 64 abuts and is surrounded by thefluorinated material 56, wherein each of the second plurality of regions64 includes silver.

That is, the second plurality of regions 64 may also be situated withinand along the monolayer 58. In one embodiment, the second plurality ofregions 64 may be equally spaced apart from each other along the firstsurface 36. In other embodiments, the second plurality of regions 64 maybe randomly spaced throughout the monolayer 58 along the first surface36. In still other embodiments, the second plurality of regions 64 maybe arranged in a pattern within the monolayer 58. The second pluralityof regions 64 may be present in the self-cleaning film 34 in an amountof from about 10 parts by volume to about 85 parts by volume based on100 parts by volume of the self-cleaning film 34, e.g., about 25 partsby volume based on 100 parts by volume of the self-cleaning film 34.

The silver may be characterized as a nanoparticle and may have anaverage diameter measureable on a nanometer scale. Alternatively, thesilver may be characterized as a particle and may have an averagediameter measureable on a micrometer scale. Generally, the silver may bepresent in the self-cleaning film 34 in an amount of from about 2 partsby volume to about 35 parts by volume based on 100 parts by volume ofthe self-cleaning film 34. The silver may provide the self-cleaning film34 with anti-microbial and air-purifying properties and soil-resistance.For example, the silver may disrupt microbe cellular function. Inparticular, the silver may contribute to phospholipid decomposition suchthat a microbe cell well cannot undergo respiration.

Referring now to FIG. 4, the monolayer 58 may have a texture 66 definedby a combination of a plurality of microstructures 68 and a plurality ofnanostructures 70. More specifically, the plurality of microstructures68 may be spaced apart from one another along the monolayer 58, and theplurality of nanostructures 70 may be disposed on each of the pluralityof microstructures 68. Further, each of the plurality of microstructures68 may have a conical shape and a first height 72 of from 0.5 μm to 2μm, e.g., 1 μm. Each of the plurality of nanostructures 70 may have asecond height 74 of from 1 nm to 4 nm, e.g., 2 nm. The texture 66defined by the combination of the plurality of microstructures 68 andthe plurality of nanostructures 70 may form a cauliflower-like orraspberry-like, non-smooth first surface 36. In one specific embodiment,the monolayer 58 may be characterized as a textured diamond-like carbon.The plurality of nanostructures 70 disposed on the plurality ofmicrostructures 68 may form a hierarchical, stochastic structure ortexture 66 that contributes to the self-cleaning capabilities of theself-cleaning film 34. The plurality of microstructures 68 and theplurality of nanostructures 70 together may increase the contact angle50 (FIG. 2) with water and oils such that the self-cleaning film 34exhibits excellent soil-resistance and minimal wettability.

That is, the contact angle 50 may be inversely related to a surfaceenergy of the first surface 36. In other words, the contact angle 50 mayincrease as the surface energy of the first surface 36 decreases. Inaddition, as the contact angle 50 increases, the first surface 36 maybecome comparatively less wettable and more hydrophobic. Since theself-cleaning film 34 has the texture 66 defined by the plurality ofmicrostructures 68 and the plurality of nanostructures 70, theself-cleaning film 34 may define the contact angle 50 with water ofgreater than 140°, e.g., greater than 150°, and the first surface 36 maytherefore be both superoleophobic and superhydrophobic.

Referring now to FIG. 5, a method 76 of forming the self-cleaning filmsystem 10, 110 includes depositing 78 the anti-reflection film 16 ontothe substrate 12. More specifically, depositing 78 the anti-reflectionfilm 16 may include magnetron sputtering 80 the first sheet 18 (FIG. 2)formed from titanium dioxide, magnetron sputtering 180 the second sheet20 (FIG. 2) formed from silicon dioxide onto the first sheet 18, andmagnetron sputtering 280 the third sheet 22 (FIG. 2) formed fromtitanium dioxide onto the second sheet 20. In another embodiment,depositing 78 may also include magnetron sputtering the fourth sheet 24formed from silicon dioxide onto the third sheet 22. Magnetronsputtering 80, 180, 280 may include accumulating the first, second, andthird sheets 18, 20, 22 using rotary or planar targets. Depositing 78the anti-reflection film 16 may form alternating sheets 18, 20, 22 asshown in FIG. 2.

The method 76 further includes magnetron sputtering 380 theself-cleaning film 34 on the anti-reflection film 16. Magnetronsputtering 380 may include disposing the fluorinated material 56 ontothe anti-reflection film 16 using, for example, a carbon target and apolytetrafluoroethylene target. In particular, the method 76 may includedisposing the fluorinated material 56 selected from the group consistingof fluorinated organic compounds, fluorinated inorganic compounds, andcombinations thereof onto the anti-reflection film 16. For example, themethod 76 may include disposing fluorinated diamond-like carbon onto theanti-reflection film 16. Alternatively, the method 76 may includedisposing fluorinated tin (IV) oxide onto the anti-reflection film 16.The fluorinated material 56 may be magnetron sputtered onto the firstlayer 18 in a suitable manner. For example, magnetron sputtering 380 maybe reactive using a planar target or a rotary target.

After magnetron sputtering 80, the method 76 also includes reactive ionetching 82 the self-cleaning film with SF₆—O₂ gas to produce the texture66 (FIG. 4) defined by the plurality of microstructures 68 spaced apartfrom one another along the monolayer 58 and the plurality ofnanostructures 70 disposed on each of the plurality of microstructures68. Reactive ion etching 82 may include varying and optimizing one ormore of a relative flow rate of SF₆ gas and O₂ gas, a pressure, and anetch time to obtain the plurality of microstructures having thegenerally conical shape, the first height 72 of about 1 μm, and a coneangle of about 50°. More specifically, reactive ion etching 82 mayinclude forming each of the plurality of microstructures 68 to have theconical shape 84 and the first height 72 of from 0.5 μm to 2 μm, andforming each of the plurality of nanostructures 70 to have the secondheight 74 of from 1 nm to 4 nm. Further, reactive ion etching 82 mayinclude minimizing a deposition energy during magnetron sputtering 80.

During use of the self-cleaning film system 10, 110, an operator maydeposit fingerprints, squalene, organic matter, and/or oils onto thefirst surface 36 (FIG. 2). Oils may include oils of fatty acids and maybe synthesized naturally and applied to first surface 36 as the operatortouches the first surface 36, or may be applied to the first surface 36artificially such as by spraying or coating.

Contact between the squalene, the photocatalytic material 54 which isexposed to electromagnetic radiation emitted by a light source having awavelength of less than 357 nm, and water may initiate formation ofradicals. The radicals may then react with hydrocarbon debris. Morespecifically, the photocatalytic material 54 may be a photocatalyst suchas titanium dioxide. A photocatalytic reaction may create a strongoxidation agent and breakdown the organic matter, e.g., squalene, to lowchain hydrocarbon to carbon dioxide and water in the presence of thephotocatalyst, i.e., the photocatalytic material 54; electromagneticradiation, e.g., ultraviolet light; and water, e.g., humidity fromambient conditions. As such, the photocatalytic material 54 may not beconsumed by the catalytic reaction, but may instead solely acceleratethe photocatalytic reaction as a non-reactant.

In greater detail, when electromagnetic radiation having a desiredwavelength illuminates the photocatalytic material 54, an electron fromthe valence band of the photocatalytic material 54 may promote to theconduction band of the photocatalytic material 54, which in turn maycreate a hole in the valence band and an excess of negative charge orelectron in the conduction band. The hole may assist oxidation and theelectron may assist reduction. Generally, the hole may combine withwater to produce a hydroxyl radical (.OH). The hole may also reactdirectly with squalene or other organic material to increase an overallself-cleaning efficiency of the self-cleaning film system 10, 110.Similarly, oxygen in the ambient environment surrounding thephotocatalytic material 54 may be reduced by the electron to form asuperoxide ion (.O₂—) which in turn may oxidize the organic materialpresent on the self-cleaning film system 10, 110.

In addition, the hole may become trapped before recombination with theelectron. For such situations, the photocatalytic material 54 may befunctionalized. For example, titanium dioxide may be doped with, forexample, palladium or ruthenium. The palladium or ruthenium may act asan electrocatalyst and may increase a transfer of electrons to oxygenmolecules, which may in turn lower the occurrence of the recombinationof electrons and holes.

Further, organic material that is present on the fluorinated material 56rather than in direct contact with the photocatalytic material 54 may bein dynamic equilibrium with the first surface 36 (FIG. 2) and maydiffuse toward a comparatively higher-energy location on theself-cleaning film 34, i.e., the photocatalytic material 54. Therefore,the self-cleaning film 34 may diffuse the squalene along theself-cleaning film 34 from the fluorinated material 56 to thephotocatalytic material 54. To improve such diffusion, the light source52 may be tuned to emit electromagnetic radiation having a wavelengththat is tuned to a vibration resonance of the squalene and thefluorinated material 56. Such tuning may enable the squalene orfingerprint to wiggle or translate along the fluorinated material 56 tothe photocatalytic material 54 where the squalene may undergo thephotocatalytic reaction described above. Alternatively or additionally,the self-cleaning film 34 may also be heated, for example by infraredradiation, to further improve diffusion across the fluorinated material56 towards the photocatalytic material 54.

Once the squalene contacts the photocatalytic material 54, the squalenemay be photolyzed into comparatively low vapor pressure-sized pieces orparts, which may vaporize off the self-cleaning film 34 and therebyremove the fingerprint or squalene from the self-cleaning film 34.Therefore, the self-cleaning film 34 may protect the substrate 12 byremoving, e.g., oxidizing and vaporizing the fingerprints, squalene,oils, and/or organic material deposited by the touch of an operator.Consequently, the self-cleaning film system 10, 110 may provideexcellent aesthetics, cleanliness, and readability for display systems,lenses, sensors, and surfaces.

While the best modes for carrying out the disclosure have been describedin detail, those familiar with the art to which this disclosure relateswill recognize various alternative designs and embodiments forpracticing the disclosure within the scope of the appended claims.

What is claimed is:
 1. A self-cleaning film system comprising: asubstrate; and an anti-reflection film disposed on the substrate andincluding: a first sheet formed from titanium dioxide; a second sheetformed from silicon dioxide and disposed on the first sheet; and a thirdsheet formed from titanium dioxide and disposed on the second sheet; aself-cleaning film disposed on the anti-reflection film and including: amonolayer disposed on the third sheet and formed from a fluorinatedmaterial selected from the group consisting of fluorinated organiccompounds, fluorinated inorganic compounds, and combinations thereof;and a first plurality of regions disposed within the monolayer such thateach of the first plurality of regions abuts and is surrounded by thefluorinated material, wherein each of the first plurality of regionsincludes a photocatalytic material.
 2. The self-cleaning film system ofclaim 1, wherein the fluorinated material is fluorinated diamond-likecarbon.
 3. The self-cleaning film system of claim 1, wherein themonolayer has a texture defined by a combination of a plurality ofmicrostructures and a plurality of nanostructures.
 4. The self-cleaningfilm system of claim 1, wherein the anti-reflection film furtherincludes a fourth layer disposed on the third layer and formed fromsilicon dioxide.
 5. The self-cleaning film system of claim 1, whereinthe first sheet has a first thickness, the second sheet has a secondthickness that is greater than the first thickness, and the third sheethas a third thickness that is greater than the first thickness and thesecond thickness.
 6. The self-cleaning film system of claim 1, whereinthe self-cleaning film has a first surface and a second surface spacedopposite the first surface and abutting the anti-reflection film, andfurther wherein the first surface is substantially free from squaleneand water.
 7. The self-cleaning film system of claim 6, wherein thesubstrate has: a proximal surface abutting the anti-reflection film; adistal surface spaced opposite the proximal surface; a first edgeconnecting the proximal surface and the distal surface; and a secondedge spaced opposite the first edge; and further including a lightsource disposed adjacent the first edge and configured for emittingelectromagnetic radiation.
 8. The self-cleaning film system of claim 7,wherein the electromagnetic radiation has a wavelength of from 400 nm to100 nm.
 9. The self-cleaning film system of claim 7, wherein theelectromagnetic radiation has a wavelength of from 740 nm to 380 nm. 10.The self-cleaning film system of claim 1, wherein the self-cleaning filmdefines a contact angle with water of greater than 140°.
 11. Theself-cleaning film system of claim 1, wherein the photocatalyticmaterial is titanium dioxide and present in the first plurality ofregions in a rutile form.
 12. The self-cleaning film system of claim 1,wherein the photocatalytic material is titanium dioxide and is presentin the first plurality of regions in an anatase form.
 13. Theself-cleaning film system of claim 1, wherein the photocatalyticmaterial is titanium dioxide and is present in the first plurality ofregions as a combination of a rutile form and an anatase form.
 14. Theself-cleaning film system of claim 1, wherein the photocatalyticmaterial is doped with silver.
 15. The self-cleaning film system ofclaim 1, further including a second plurality of regions disposed withinthe monolayer such that each of the second plurality of regions abutsand is surrounded by the fluorinated material, wherein each of thesecond plurality of regions includes silver.
 16. A self-cleaning filmsystem comprising: a substrate; and an anti-reflection film disposed onthe substrate and including: a first sheet formed from titanium dioxide;a second sheet formed from silicon dioxide and disposed on the firstsheet; and a third sheet formed from titanium dioxide and disposed onthe second sheet; a self-cleaning film disposed on the anti-reflectionfilm and including: a monolayer disposed on the third sheet and formedfrom a fluorinated material selected from the group consisting offluorinated organic compounds, fluorinated inorganic compounds, andcombinations thereof; wherein the monolayer has a texture defined by: aplurality of microstructures spaced apart from one another along themonolayer; and a plurality of nanostructures disposed on each of theplurality of microstructures; and a first plurality of regions disposedwithin the monolayer such that each of the first plurality of regionsabuts and is surrounded by the fluorinated material, wherein each of thefirst plurality of regions includes a photocatalytic material.
 17. Theself-cleaning film system of claim 16, wherein each of the plurality ofmicrostructures has a conical shape and a first height of from 0.5 μm to2 μm and further wherein each of the plurality of nanostructures has asecond height of from 1 nm to 4 nm.
 18. The self-cleaning film system ofclaim 16, wherein the anti-reflection film further includes a fourthlayer disposed on the third layer and formed from silicon dioxide.
 19. Amethod of forming a self-cleaning film system, the method comprising:depositing an anti-reflection film on a substrate, wherein theanti-reflection film includes: a first sheet formed from titaniumdioxide; a second sheet formed from silicon dioxide and disposed on thefirst sheet; and a third sheet formed from titanium dioxide and disposedon the second sheet; magnetron sputtering a self-cleaning film on theanti-reflection film, wherein the self-cleaning film includes: amonolayer disposed on the third sheet and formed from a fluorinatedmaterial selected from the group consisting of fluorinated organiccompounds, fluorinated inorganic compounds, and combinations thereof;and a first plurality of regions disposed within the monolayer such thateach of the first plurality of regions abuts and is surrounded by thefluorinated material, wherein each of the first plurality of regionsincludes a photocatalytic material; and after magnetron sputtering,reactive ion etching the self-cleaning film with SF₆—O₂ gas to produce atexture defined by: a plurality of microstructures spaced apart from oneanother along the monolayer; and a plurality of nanostructures disposedon each of the plurality of microstructures.
 20. The method of claim 19,wherein reactive ion etching includes forming each of the plurality ofmicrostructures to have a conical shape and a first height of from 0.5μm to 2 μm and forming each of the plurality of nanostructures to have asecond height of from 1 nm to 4 nm.